Multimedia teleconferencing provides a way for people at distant locations to simulate a live, face-to-face meeting and commonly involves the two-way, real-time transmission of audio, video, an other data between two or more participating sites. Generally, a computer, video camera, and speaker are employed at each site participating in a video conference. Teleconferencing software executing on each computer manages the equipment and the conferencing session. The session is often interactive in that it allows participants to make changes to documents that others can see in real-time. A windows-based graphical user interface is often employed so that live video can be seen by a user in one window, while other computer-generated images are displayed in other windows. The participating computer systems may be connected by any of various types of communication links, such as conventional telephone lines, otherwise known as Plain Old Telephone Service (POTS), a local area network (LAN), or Integrated Services Digital Network (ISDN) connections.
One problem that is associated with multimedia teleconferencing relates to the transfer of images between participating sites, such as during "white board" image sharing. Specifically, image files are often very large and require a large amount of bandwidth to transmit from one computer system to another. As a result, transmission of an image from one computer system to another often consumes an undesirably large amount of time, during which the transmitting system, the receiving system, or both may be unable to perform other tasks or may be noticeably slowed down. In addition, transmission of a large image file may adversely impact the quality of associated audio and video transmissions by consuming available bandwidth. These factors can undesirably extend the duration of a teleconference and detract from the usefulness and enjoyment of a teleconference for the participants. In addition, awareness the above factors may cause a teleconference participant to be overly selective about transmitting images to other participants, which may further limit the effectiveness of the teleconference.
Moreover, it may be difficult for a conference participant to predict whether transmission of an image will have any of the foregoing undesirable effects and, if so, to what extent. The transfer of a large image file may occur within a very reasonable amount of time when the available bandwidth is high but consume an unacceptably long amount of time when the available bandwidth is low, such as during peak usage hours. Consequently, a participant's decision whether to transmit an image may be little more than an educated guess, based perhaps on knowledge of the image file size and an estimate of the currently available bandwidth. The result is often the incorrect decision from the point of view of at least one participant. Hence, what is needed is a technique for increasing the perceived bandwidth of a data communication link between computer systems, so as to allow for improved transfer of images in various applications, such as multimedia teleconferencing.